This invention relates to a balancer shaft for a four cycle engine and more particularly to an improved mounting structure for such a shaft.
It is well known that reciprocating engines generate certain forces which should be balanced to provide smooth running. One way in which these forces are balanced is by providing a balancing shaft having eccentric masses which is driven by the crankshaft and which rotates at the same speed as the crankshaft but in an opposite direction. Although such balancing shafts have high utility and provide smooth running engines, the addition of a further shaft to the engine crankshaft complicates and enlarges the overall construction of the engine.
Conventionally it has been the practice to locate the balance shafts on the side of the engine crankshaft so as to avoid any increase in height of the overall engine. It is undesirable for a number of reasons to increase the height of the engine. An increase in height not only raises the center of gravity in the overall vehicle but also precludes the use of low hood lines which are important for aerodynamic reasons.
When the balance shaft is employed in a four cycle internal combustion engine additional problems arise. For instance, if the balancer shaft is located at a distance away from the crankshaft, the intermediate area, that area between the crankshaft and the balance shaft, will be subject to the vibrations caused by the imbalance. The vibrations are then translated into other components causing both vibrations and noise, both of which are undesirable. Another problem arises when the balance shaft is located in the oil collection region of the oil pan. When the rotating balance shaft contacts the oil, the oil will froth which could potentially cause damage to the oil pump.
It is therefore a principal object of this invention to provide an improved balance shaft mounting arrangement for an internal combustion engine.
It is a further object of this invention to provide a balance shaft mounting arrangement that does not increase the overall height of the engine.
It is yet a further object to this invention to provide an improved balance shaft arrangement for a four cycle engine wherein the balance shaft rotates within the crankcase chamber and is positioned closely adjacent to the crankshaft.